What is the correct ISCN nomenclature for a male with fragile X syndrome?

The correct International System for Human Cytogenetic Nomenclature (ISCN) for a male with fragile X syndrome is represented as 46,XY,fra(X)(q27.3). This notation provides specific information about the individual's chromosomal structure.

In this nomenclature:

• "46" represents the total number of chromosomes, indicating a normal diploid count.
• "XY" specifies the sex chromosomes, indicating that the individual is male (one X and one Y chromosome).
• "fra(X)" denotes the presence of a fragile site on the X chromosome, which is critical for identifying fragile X syndrome.
• The designation "(q27.3)" provides precise localization of the fragile site, specifying that it is located on the long arm (q) of chromosome X at position 27.3.

This level of detail is essential in clinical genetics for identifying specific genetic conditions and understanding their underlying mechanisms. The designation of the fragile site at q27.3 is significant because fragile X syndrome is associated with a CGG repeat expansion in the FMR1 gene, which is located at this specific cytoband of the X chromosome.

The other choices lack either the correct chromosome count, sex designation, or precise localization of the fragile site